I’m using Fedora 15.x86, as the yum mainline may not update in a few while(it may be outofdate… )
Following packages help..
http://kojipkgs.fedoraproject.org//packages/xulrunner/13.0.1/1.fc15/i686/xulrunner-13.0.1-1.fc15.i686.rpm
http://kojipkgs.fedoraproject.org//packages/xulrunner/13.0.1/1.fc15/i686/xulrunner-devel-13.0.1-1.fc15.i686.rpm
http://kojipkgs.fedoraproject.org//packages/firefox/13.0.1/1.fc15/i686/firefox-13.0.1-1.fc15.i686.rpm